Where is the heat escaping?
Heat loss in heated buildings can be determined using exact methods. Most heat usually escapes through the external walls, although this will vary considerably depending on the type of building. This can be as much as 30-40% of the total heat loss. Heat loss through the roof is of a similar order of magnitude. In this negative order, the openings, plinth zone, floor and slabs are next.

The amount of heat loss is essentially determined by the heat transfer coefficient of the structural elements and the materials used in the insulation system. This depends, among other things, on the material and thickness of the walls and individual elements, the number of layers of render, the quality of the insulation and the method of construction.
Energy classification of buildings

Since 1 January 2016, buildings in Hungary are classified from energy class AA++ to JJ according to the relevant legislation. The classification is based on the building's energy performance certificate, which is based on the estimated annual energy demand of the building, as verified by calculations. The calculation of the energy demand takes into account the material and quality of the building structure, the type of insulation used in the different structural parts (masonry, slab, basement) and the mechanical installations in the building. The higher the category of building, the less energy is needed to use and operate it.

Statistical information can also be obtained from the energy performance certificates produced under the new classification system and uploaded to the National Register of Buildings. Based on the information downloaded from the above database, more than 1,100,000 certificates were uploaded between 2016 and 2022, giving the following breakdown of the classification of buildings classified:

Based on the chart, a total of 4.6% of the certified buildings meet the minimum BB rating for the occupancy permit. The majority of the certified buildings fall into the CC category. This may be due to the fact that only buildings that also use renewable energy sources in their operation can be rated better than BB. 

Thermal insulation properties of wall types

The relationship between the thermal transmittance of different types of wall construction and the energy demand of a building is shown in the table below. Four types of walls are compared: the uninsulated wall made of B30 bricks, popular in the 1980s, the version with a 5 cm thermal insulation layer, as required in the 2000s, the same with a 15 cm thermal insulation layer from 2015, and finally the type with a 25 cm thermal insulation layer, as required by the current passive house regulations. The energy demand was calculated on the basis of average winter outside temperatures and an inside temperature of 21 degrees Celsius, with the passive house as the unit.

Energy requirements for new build

After 1 July 2024, only new build houses with "near-zero energy demand" will be allowed to be put into use. This means that the building is rated at least BB according to the energy performance certificate. To achieve BB, the overall energy performance of the building must not exceed 100 KWh/m2/year and at least 25% of its energy use must come from renewable energy sources. In addition, the specific heat loss factor for the building as a whole shall not exceed 100 kWh/m2 per year. 

The above should also be taken into account for renovations in certain situations. 

The requirements for the minimum thermal insulation performance of the building structure, introduced in 2018, have not been tightened. For wall constructions bordering heated spaces, this heat transfer coefficient should not be higher than 0.24 W/m2K (U-value). How this value is achieved is not regulated. For different types and sizes of wall constructions, calculations can be made to determine the type and size of insulation required, taking into account the additional needs of the client. The Thermal Insulation Calculator available on the website of CEMIX Hungary Ltd.